Compared with the Cathode-Ray Tube (CRT) display devices that are widely used in early stage, the Liquid Crystal Displays (LCDs) have the advantages of a light and thin structure, low driving voltage, and low power consumption. Therefore, the LCD devices, especially the active array LCDs are widely used in various electronic apparatuses. In the active array LCD, Thin Film Transistors (TFTs) are arranged to serve as the switching elements for the sub pixels, and enable that the display performance of the LCD can match the CRT display devices with high driving performance.
FIG. 1 schematically shows a structure of an LCD in the prior art.
As shown in FIG. 1, an LCD 100 comprises a first substrate 101, a second substrate 103, and a liquid crystal layer 102 that is arranged between the first substrate 101 and the second substrate 103. The liquid crystal layer 102 comprises liquid crystal molecules 104. The second substrate 103 is provided with a plurality of data lines and a plurality of scanning lines, wherein the data lines as well as the scanning lines cross over with each other so as to form pixel areas. However, in actual situations, in addition to the liquid crystal molecules 104, the liquid crystal layer 102 may further comprise impurity molecules 105, which can have a positive polarity or a negative polarity.
FIG. 2 schematically shows a driving principle of a liquid crystal display panel in the prior art. As shown in FIG. 2, when a gate voltage (i.e., a voltage of a corresponding scanning line) of a TFT changes so that a source and a drain of the TFT are electrically connected with each other, a data line would transmit a data signal to a pixel electrode, and the voltage of the pixel electrode would change (for example, change from a low-level voltage to a high-level voltage). At the same time, the voltage change of the gate of the TFT would generate a feed through voltage on the pixel electrode. In order to balance the data signals at the two ends of the common voltage Vcom, according to the method in the prior art, the common voltage is generally reduced with a certain amount accordingly (i.e., the common voltage Vcom is changed from a dotted line to a solid line as shown in FIG. 2) so as to avoid an excessive direct current bias voltage.
However, there would still be a certain direct current bias voltage in different liquid crystal display panels and different areas of the same liquid crystal display panel after long time driving because of the differences of the manufacturing process, signal transmission loss, human-caused error, and other factors. In this case, when the liquid crystal display panel is activated for a long time, the impurity molecules in the liquid crystal display panel would move under the action of the direct current bias voltage, and thus an afterimage would be generated.
The afterimage level has become an important indicator for measuring the quality of the liquid crystal display panel. In order to improve the quality of the liquid crystal display panel, on the basis of the regulation of the common voltage Vcom, there are many methods in the prior art for alleviating the afterimage of the liquid crystal display panel, including optimizing the manufacturing environment and condition, optimizing material selection, and optimizing the gamma voltage.
Optimizing the manufacturing environment and condition means removing impurities away from the liquid crystal display panel or preventing the external impurities from entering into the panel during the manufacturing process mainly through guaranteeing a dust-free environment during manufacturing, shortening manufacturing time, cleaning the substrate before One Drop Filling (ODF) and drying quickly after cleaning so as to alleviate the afterimage of the display panel.
Optimizing material selection means reducing the impurities of the liquid crystal display panel through selecting suitable polyimide (PI) material and Liquid Crystal (LC) material, selecting sealing material with low pollution, selecting LC material with good stability and with a low content of polar particles, and so on.
Optimizing the gamma voltage means determining the optimized IS monochrome voltage through regulating the gamma voltage, reducing the differences between common voltages Vcom at different positions of the liquid crystal display panel, and reducing the differences between common voltages Vcom of different gray-scales, so as to reduce the maximum direct current bias voltage between the pixel electrodes and the common electrodes of the liquid crystal display panel after long time activation to the largest extent and alleviate the afterimage of the liquid crystal display panel.
However, according to the methods in the prior art, the afterimage of the liquid crystal display panel can only be alleviated to a rather limited extent, and the display effect thereof cannot be improved effectively.